(a) Field of the Invention
The present invention relates to a system for traffic signals for one side passing, having two-position signal temporarily provided at both ends of a road section under construction.
(b) Description of Prior Art
Generally, in the event that vehicles alternately pass a one-side road section under construction from opposite directions, traffic signals are temorarily provided at both ends of the section, thereby conducting a traffic control. One of the representative of such prior art is disclosed, for example, in Japanese Patent Appln Laid-Open No. 3-62198, wherein at both ends of the section are provided traffic signals and detector means such as pressure sensors for detection of the number of vehicles passing therethrough, thus extending the lighting time of green signals at the heavier traffic end. Likewise, there is disclosed a signal controller circuit in Japanese Utility Model Publication No. 55-31675, while there is also disclosed a signal device which changes indication of signals by means of vehicle detector means such as light sensor or the like provided adjacent the signals in Japanese Utility Model Appln Laid-Open No. 64-27798. Further, there is further disclosed a system for alternately switching traffic signals controller device in Japanese Patent Appln Laid-Open No. 5-40897, having a set of traffic signals which is so operated that while one traffic light at passage allowed end is green, the other traffic signal at no passage allowed end is red or against us and detector means for detection of vehicles passing through the section. Furthermore, there is also proposed a traffic signal device provided at both ends of a road section under construction in Japanese Patent Publication No. 50-13120.
However, according to the traffic signals controller device in Japanese Patent Appln Laid-Open No. 3-62198, as the device controls the lighting time of the traffic signal based on the numeric data concerning waiting vehicles, it is difficult to allow vehicles from opposite directions to efficiently pass the section to shorten the waiting time of vehicles. Further, according to any of the above prior art, the waiting time will become still comparatively long, thus easily causing a traffic jam when traffic density is distinctly large at one side than at the other side in the road repairing section.
In addition, according to the above prior art, as they employ sensitive systems for control of the lighting of the traffic signals based on the detection of vehicles by the detector means such as pressure sensor, light sensor or the like, the control systems for traffic signals will be damaged in case of troubles being caused in the detector means. Furthermore, as such signal systems are usually still in operation even at night when no vehicles are found, there will sometimes be no input of detection signals for more than a preset time. In such case, you cannot conclude merely from the fact of no traffic that the detector means are out of order. Additionally, according to the above prior art, vehicles from the opposite directions will be exposed to great danger of head-on collision in the case that a vehicle enters the section against a red signal immediately after the change to red from green, while another vehicle also enters the section because of the signal change to green from red before the passing of the opposite vehicle.